In the conventional clutch cover assembly, a pressure plate 7 is connected to a clutch cover 2 by a strap plate 21 and a diaphragm spring 8 is contacted with a fulcrum boss 7a formed integrally with the pressure plate 7, as illustrated in FIG. 5.
In this structure, it is required to ensure a wear-in allowance D by a load characteristic as diagrammed in FIG. 6. However, there is a limitation on a range of the wear-in allowance D so that, when a wear amount of a facing 6 increases, the diaphragm spring 8 is inclined to such an extent that an outer peripheral end portion of the diaphragm spring is near to the pressure plate 7 side when the clutch is engaged. The load characteristic is thereby decreased so that the facing can not be utilized fully to its maximum wear amount.
In order to increase the wear-in allowance and prolong service life of the facing, the applicant of this invention has proposed, in Published Patent Application (KOKAI) No. 63-270925 for example, a clutch cover assembly capable of automatically increasing height of a fulcrum point portion with an increase in a wear of the facing. In this structure, a fulcrum point portion, contacting with a diaphragm spring, is divided into two inside and outside fulcrum rings so that the fulcrum rings are pushed up to the diaphragm spring side, with an increase in wear of the facing, by means of actions of a slide key and spring.
However, because the slide key is fitted in the pressure plate, so as to be movable in a radial direction, the fulcrum rings are sometimes pushed up excessively y centrifugal force caused by rotation of the clutch, so that it is difficult to adjust weights of the fulcrum rings and the slide key.